The reactivity of ethyl iodides on hydrogen predosed Ni(100) surfaces
has been studied by using temperature programmed desorption (TPD) spec
troscopy. The data show that hydrogen coadsorption inhibits the decomp
osition of ethyl groups at all coverages. Also, at ethyl iodide covera
ges below saturation, the yields of both ethylene and ethane (the prod
ucts of beta-hydride and reductive elimination reactions respectively)
increase equally with hydrogen coadsorption, but near saturation the
desorption of ethane increases at the expense of ethylene production.
A small amount of ethane is also produced via the hydrogenation of che
misorbed ethylene. This latter reaction occurs at higher temperature,
which means that its activation energy is higher than that for the dir
ect hydrogenation of the ethyl species. No coupling or H-D exchange re
actions were observed in our experiments.